The project has two major objectives. The first is the application of the agar culture technique for detection of quantitative and qualitative defects in granulocytic stem cells (CFU-c) in the marrow of patients with leukemia and myeloproliferative disorders in both the untreated phase and during the course of therapy. This screening protocol is designed to provide detailed information of diagnostic and prognostic value. The second major objective evolves from this screening programme and is aimed at investigating (1) the nature of the cellular and regulatory lesions in leukemia; (2) the interaction between normal and leukemic hematopoietic cell populations during the development and treatment of the disease. BIBLIOGRAPHIC REFERENCES: Moore, M.A.S. Marrow culture - a new approach to classification of leukemias. Blood Cells 1:149-158 (1975). Moore, M.A.S. Embryologic and phylogenetic development of the hematopoietic system. Advances in the Biosciences, the Myelofibrosis-Osteosclerosis Syndrome, 16:87-101. Pergamon Press. (1975).